This invention relates to a tubing string rotator, and in one particular embodiment a rotator that may be attached to a wellhead and used to suspend and rotate a tubing string within a wellbore.
Fluids that are pumped from wellbores utilizing a downhole pump are typically transported to the surface through the use of a tubing string. It is well known that to minimize wear on the surface of the tubing string through contact with the pump rod, and to extend the useful life of the string, a tubing string rotator may be used to slowly rotate the string within the well casing and to more evenly distribute wear about the surface of the string.
Tubing string rotators that have been developed and put into practice to date have a wide variety of different configurations and structures. In most instances the rotator acts as both a hanger to suspend the string within the well casing, and as a means to impart rotational movement to the tubing string. In order to cause the string to revolve within the casing, rotators commonly utilize a mechanical linkage connecting a series of gears or a drive system to a tubing string hanger. The mechanical connection between the drive system and the hanger is often in the form of either a key or a series of interlocking splines. Unfortunately, when using a keyed or splined connection alignment between adjacent parts is critical. In the case a keyed connection misalignment will prevent insertion of the key. When a splined connection is used misalignment could potentially result in damage to the splines or may cause the hanger and string to become jammed within the rotator. In addition, where the fluids that are being extracted from the well contain a high degree of sand or particulate matter, debris can often find its way into small spaces between the splines or adjacent to the key. Sand or other particulate material that becomes lodged within these areas can cause the entire structure to lock together. In such cases it can become extremely difficult (if not virtually impossible) to remove the hanger from the rotator.
The invention therefore provides a tubing string rotator that facilitates the insertion and removal of a tubing string hanger from the rotator. The invention allows for the rapid insertion and removal of the tubing string hanger, while at the same time eliminating the risk and the potential damage that may be caused by misalignment of the hanger with the internal drive system of the rotator. In addition, the invention provides a tubing string rotator that helps to facilitate the removal of a tubing string hanger in situations where well fluids contain a high degree of sand and other particulate material.
Accordingly, in one of its aspects the invention provides tubing string rotator comprising; an outer housing having an upper end and a lower end with an internal bore extending therethrough from said upper to said lower end; a gear mandrel receivable and supportable within said internal bore of said outer housing, said gear mandrel having an upper end and a lower end and an internal surface that defines an internal bore extending through said gear mandrel from said upper to said lower end; and, a tubing string hanger having an upper end, a lower end and an external surface, said external surface of said tubing string hanger having a series of circumferentially positioned generally downwardly oriented teeth, said tubing string hanger receivable and suspendable within said internal bore extending through said gear mandrel such that said teeth on said tubing string hanger engage a series of generally upwardly oriented teeth circumferentially positioned about said internal surface of said gear mandrel whereby rotational force applied to said gear mandrel is at least partially transferred to said tubing string hanger through engagement of said generally upwardly and said generally downwardly oriented teeth causing said tubing string hanger to rotate with said gear mandrel.
In a further aspect the invention provides tubing string rotator comprising; an outer housing having a generally hollow interior and having an internal bore extending through said housing from an upper end to a lower end of said housing; a gear mandrel receivable within said hollow interior of said outer housing, said gear mandrel having an upper end and a lower end and an internal surface that defines an internal bore extending through said gear mandrel from said upper to said lower end; a drive gear engaging said gear mandrel such that rotation of said drive gear causes rotation of said gear mandrel about an axis generally parallel to said internal bore extending through said gear mandrel; and, a tubing string hanger receivable and suspendable within said internal bore of said gear mandrel, said tubing string hanger having an external surface having mounted thereon a plurality of circumferentially positioned generally downwardly oriented teeth, said generally downwardly oriented teeth engaging a plurality of compatibly shaped generally upwardly oriented teeth circumferentially positioned about said internal surface of said gear mandrel when said tubing string hanger is received without said gear mandrel such that said tubing string hanger may be rotated through the transference of rotational force applied to said gear mandrel to said tubing string hanger through engagement of said generally upwardly and said generally downwardly oriented teeth.
In yet a further aspect the invention concerns a tubing string rotator comprising; an outer housing having an upper end and a lower end, said lower end adapted to be received upon an oil well casing or wellhead, said outer housing having an internal bore extending therethrough from said upper end to said lower end; a gear mandrel received and supported within said internal bore of said outer housing, said gear mandrel having an internal surface that defines an internal bore extending therethrough, said internal surface of said gear mandrel including a reduced diameter portion having circumferentially positioned thereabout a plurality of generally upwardly oriented teeth; and, a tubing string hanger receivable and suspendable within said internal bore through said gear mandrel, said tubing string hanger having an exterior surface containing a plurality of circumferentially positioned generally downwardly oriented teeth engagable with said generally upwardly oriented teeth of said gear mandrel when said tubing string hanger is received within said internal bore in said gear mandrel such that rotational force applied to said gear mandrel is at least partially transferred to said tubing string hanger through engagement of said generally upwardly and said generally downwardly oriented teeth causing said tubing string hanger to rotate with said gear mandrel, and wherein at least a portion of the weight of said tubing string hanger is transmitted to and borne by said gear mandrel through engagement of said generally upwardly and said generally downwardly oriented teeth.